/*
 * Copyright (C) 2011 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.util.concurrent;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.GwtCompatible;
import java.util.concurrent.Executor;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;

/**
 * A {@link Future} implementation which always throws directly from calls to {@code get()} (i.e.
 * not wrapped in {@code ExecutionException}. For just a normal failure, use
 * {@link SettableFuture}).
 *
 * <p>
 * Useful for testing the behavior of Future utilities against odd futures.
 *
 * @author Anthony Zana
 */
@GwtCompatible
final class UncheckedThrowingFuture<V> implements ListenableFuture<V> {
    private final Error error;
    private final RuntimeException runtime;

    public static <V> ListenableFuture<V> throwingError(Error error) {
        return new UncheckedThrowingFuture<V>(error);
    }

    public static <V> ListenableFuture<V> throwingRuntimeException(RuntimeException e) {
        return new UncheckedThrowingFuture<V>(e);
    }

    private UncheckedThrowingFuture(Error error) {
        this.error = checkNotNull(error);
        this.runtime = null;
    }

    public UncheckedThrowingFuture(RuntimeException e) {
        this.runtime = checkNotNull(e);
        this.error = null;
    }

    @Override
    public boolean cancel(boolean mayInterruptIfRunning) {
        return false;
    }

    @Override
    public boolean isCancelled() {
        return false;
    }

    @Override
    public boolean isDone() {
        return true;
    }

    @Override
    public V get() {
        throwOnGet();
        throw new AssertionError("Unreachable");
    }

    @Override
    public V get(long timeout, TimeUnit unit) {
        checkNotNull(unit);
        throwOnGet();
        throw new AssertionError();
    }

    @Override
    public void addListener(Runnable listener, Executor executor) {
        checkNotNull(listener);
        // TODO(cpovirk): Catch RuntimeExceptions
        executor.execute(listener);
    }

    private void throwOnGet() {
        if (error != null) {
            throw error;
        } else {
            throw runtime;
        }
    }
}
